[time-nuts] Accurate Thunderbolt position

Mark Sims holrum at hotmail.com
Wed Jul 15 05:48:28 UTC 2009


Well it started as a simple exercise in "Hey,  now that really I know where I am,  how close can a Tbolt get".  Well,  it looks like a foot or so may be doable.  Might be useful for something,  even if it does not help the timing application.

Then the thing showed its stupid limitation of not being able to enter a precise (double precision) location.  In fact if you figure 3 microdegrees/foot,  a 24 bit mantissa single precision floating point number will only get you to around 50 feet.  You can't arbitrarily offset your location by just a meter or two...  If you want better than 50 feet all you can do is use the self-survey results.  

Right now, I don't really care if it is useful,  I'm gonna find a way to cram a precise location into the beast, even if I have to pound it in with a sledge hammer...  then we'll see what difference it makes.  And 50 feet of error could easily be around 50 nanoseconds...

----------------------------------------


Before you spend too much time trying to nail it down to the
foot or inch you might want to see what effect being off by
a couple feet or meters actually has on your TBolt timing
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